The present invention relates generally to the identification of hot (e.g., 1,200.degree. F.) coils of steel stock, and more particularly to thermally transfer printable labels which can be readily printed and attached to the hot coil stock.
Steel coil, often called "hot bands", are rectangular sheets of steel or metal wound into coils, often with a nominal 30 inch diameter open center and typically weighing about 25 tons. Such steel coils find use in the manufacture inter alia of refrigerators, automobile bodies, and like articles. Parameters influencing the characteristics and available applications of hot bands depend upon, for example, the rolling parameters, chemistry of the steel, and like grade designations. Such grade designations will determine the particular application for which the hot band is suitable. Besides grading the coil stock for determining applications, should a particular part fail, the cause of failure often can be traced back to the chemistry, rolling parameter, or other grade designation which may reveal the cause of the part failure and/or provide information with respect to modification of requirements of the steel for the particular part or its intended use.
Presently, workers often mark hot bands while they are still hot with chalk for generating human readable characters. Alternatively, dot matrix paint characters or articulated sprays also can be used to mark the hot bands. Unfortunately, when the hot bands are stored in large yards, the handwriting or paint generated characters may be upside-down, and the steel may have rusted, obscuring the characters. Human readable characters alone do not facilitate reliable automatic identification. In regard to the marking of hot bands, it will be understood that such steel coils will be at a temperature of about 1200.degree. F. when exiting the rolling line downcoiler where it would be convenient and provide reliable information if marking occurred at such point in the manufacturing operation. Hot coils also have been marked with ceramic-coated metal tags which were printed with a dot matrix printer utilizing carbon impregnated ribbon. Such tags, however, tend to be quite thick, difficult to attach, and are printed with conventional printing equipment which is not amenable to use on the factory floor. Fiberglass tags also have been proposed. Such proposed tags were to be printed with a thermal offset printer, though their attachment to the hot coils was a problem not solved.
Thus, there exists a need to provide machine readable characters on hot bands as well as reliable human readable characters. Moreover, the need extends to marking the hot bands when they are at elevated temperature, say in the neighborhood of 1200.degree. F.